Top tech investor Shervin Pishevar is suing a Republican-led political opposition research firm in Silicon Valley for defamation, claiming that it carried out a “malicious smear campaign” against him. According to the complaint, filed in San Francisco superior court, Definers Public Affairs was hired by “one or more of his business competitors” in order to “assassinate” Pishevar’s character and to “destroy his career.” Pishevar is best known for his investments in Uber, Hyperloop One, and Munchery, as well as dozens of other startups. And he has been an aggressive defender of former Uber CEO Travis Kalanick.

Among the “false, defamatory, and highly damaging” stories spread about Pishevar by Definers founder Ben Rhoades, who worked as Mitt Romney’s campaign manager in 2012, according to the complaint:

That Pishevar is an “agent of the Russian government and a friend of Russian president Vladimir Putin,” and those connections were behind Russian investment in Hyperloop One.

That Pishevar “had an incident with a prostitute in Europe.”

That Pishevar “paid money to settle a claim for sexual assault in London.”

That Pishevar raised money for direct investment in Uber but used it to put into his own pockets and the coffers of his venture capital firm, Sherpa Capital.

The fact that Definers is led by Republican operatives is interesting, considering that Pishevar is one of the biggest Democratic donors in the Valley. In April 2016, he joined George Clooney and his wife, Amal Clooney, to host an event for Hillary Clinton at Pishevar’s home in the Nob Hill neighborhood of San Francisco. The price of admission: $353,000 per couple. The elite dinner and cocktails raised at least $2.3 million for Clinton’s presidential campaign. Since 2011, he’s personally donated $226,600 to the Democratic National Committee, as well as individual contributions to Barack Obama, Rep. Rohit Khanna, Senator Kamala Harris, and Senator Cory Booker, among others.

Tim Miller, a partner at Definers and the former communications director for Jeb Bush’s presidential campaign, strongly denied the claims in a tweet on Monday night:

Mr Pishevar’s claims are delusional. Definers has never engaged in any of the actions in his complaint nor done any work with regards to him https://t.co/Hx0O3IpVxy